Where neutrinos are born: Russian scientists are close to unraveling the origin of the smallest cosmic particles

Scientists from the Physics Institute. P.N. Lebedev RAS (LPI), Moscow Institute of Physics and Technology (MIPT) and the Institute for Nuclear Research RAS (INR RAS) for the first time established that ultrahigh-energy neutrinos are generated near black holes in the active nuclei of galaxies - quasars. This was reported in the Astrophysical Journal.

Recall that neutrinos are the smallest elementary particles propagating through the Universe at a speed that can exceed the speed of light. They are not yet sufficiently studied by science, even their exact mass is unknown. These structureless particles are harmless to living organisms, easily pass through planets and are difficult to register. A well-known source of neutrinos is the Sun, where these particles are involved in thermonuclear reactions. Neutrino streams also produce active nuclear reactors.

The existing detectors of these particles on Earth record neutrino events occurring in faraway space and possessing ultrahigh energy - more than 200 trillion electron-volts. However, their source has not yet been discovered.

• Telescope "RATAN-600" and neutrino as presented by the artist
• © MIPT, Daria Sokol

Russian scientists have come close to unraveling this issue. They compared the data of the IceCube neutrino telescope in Antarctica with radio astronomical observations of quasars, including the world's largest radio telescope, RATAN-600, located in Karachay-Cherkessia.

As a result, researchers were able to find a connection between cosmic neutrinos and flares in the centers of distant active galaxies where supermassive black holes are located. According to astrophysicists, during the attraction of matter by a black hole, part of the particle stream is thrown back, accelerated and gives rise to ultrahigh-energy neutrinos, which is accompanied by flashes of radio emission.

“Our result suggests that high-energy neutrinos are born in the active nuclei of galaxies, and it is precisely at the moments of outbreaks of radio emission. Since both these particles and radio waves propagate through the Universe at the speed of light, we “see” them on Earth at the same time, ”said the author of the work, graduate student of the Lebedev Physical Institute and Moscow Institute of Physics and Technology Alexander Plavin.

The first stage of the study was devoted to proving that the directions from which superhigh-energy neutrinos come to Earth coincide with the position of bright quasars, which was determined by radio telescopes. The second stage of the work was the confirmation of the hypothesis that ultrahigh-energy neutrinos appear in galaxies during flashes of radio emission. For this, a team of astrophysicists used data from the Russian RATAN-600 telescope on flashes on quasars and compared them with fifty neutrino events from IceCube.

“We decided to test a non-standard idea, not really counting on success. But we are lucky! It was the radio range that turned out to be the key for detecting neutrino sources, ”said astrophysicist at the Lebedev Physical Institute and Moscow Institute of Physics and Technology, corresponding member of the Russian Academy of Sciences Yuri Kovalev.

Previously, neutrino sources were searched primarily in gamma rays, since it was believed that they should be born with gamma radiation. Therefore, the results obtained by scientists at first aroused distrust.

“The result seemed“ too good. ” But, having carried out a detailed analysis of the data and numerous tests, we confirmed the clear connection of neutrino events with radio emission, which was then checked by long-term measurements of radiation flashes on the RATAN-600 radio telescope. The probability that this result is random is only 0.2%. This is a great success in neutrino astrophysics, and now our discovery requires a theoretical explanation, ”said Sergey Troitsky, chief research officer of the INR RAS, corresponding member of the Russian Academy of Sciences.

In particular, verification of the results will be carried out using the data from the Baikal-GVD telescope, which is currently being completed on Lake Baikal, scientists say.